1. Field of the Invention
The present invention relates to an adhesive mesh tape for preventing implosion of a cathode-ray tube (hereinafter referred to as xe2x80x9cCRTxe2x80x9d) and to an implosion-proof method and an implosion-proof cathode-ray tube.
2. Description of the Related Art
Since strain is produced in the walls of cathode-ray tubes with unique shapes by the extreme vacuum maintained inside the tubes, reverse strains occur, due to impacts exerted on the front of the cathode-ray tube, that cause bulges in the cathode-ray tube outer surface and eventually breakage, in extreme cases. Current implosion-proof systems for cathode-ray tubes used in television sets and the like achieve reinforcement by applying metal clamping bands onto the outer surface of the tubes.
In such systems, it is necessary for the clamping strength of the clamping band to be effectively transferred to the surface of the cathode-ray tube, and for that purpose an effective and strong adhesive member must be situated between the inside of the clamp band and the surface of the cathode-ray tube. Without provision of such an effective adhesive member, clamping of the band may lead to slipping of the band due to the curvature of the cathode-ray tube surface, thus eliminating the reinforcing effect, or direct contact of the band with the cathode-ray tube surface may damage the surface creating local weak points, or elongation over the entire bulge may be caused in the outer surface of the cathode-ray tube with the corner as the fulcrum, thus presenting a disadvantage whereby a satisfactory implosion-proof function is no longer exhibited.
On the other hand, if an effective adhesive member is present, introduction of cracks at the front of a cathode-ray tube is prevented when it is subjected to impact. Even if a crack is generated at that section, the bulge in the outer surface, produced along with the crack, is limited by a force that will elongate the band at only a very limited section of the perimeter of the crack, and therefore the crack halts directly under the clamp band and breakage is also prevented. Even if the cathode-ray tube were to break, the fragments are held by adhesion with the clamping band, so that scattering of broken glass fragments is kept to an absolute minimum.
As an implosion-proof adhesive, the present applicant (Teraoka Seisakusho K.K.) has already developed and disclosed an adhesive tape prepared by applying a hot-melt adhesive onto one side of a base with a prescribed strength, and applying a pressure-sensitive adhesive onto the other side (Japanese Examined Patent Publication (Kokoku) No. 63-24291). The applicant has also disclosed an adhesive tape prepared by filling inorganic granules of a prescribed particle size into a pressure-sensitive adhesive layer provided on both sides of a tape matrix made of a hot-melt resin (Japanese Examined Patent Publication (Kokoku) No. 1-43791). The applicant has further disclosed an adhesive tape prepared by forming a hot-melt adhesive layer on one side and a pressure-sensitive adhesive layer on the other side of a base matrix which is a union fabric employing natural or synthetic fibers as the warp component and glass filaments as the weft component (Japanese Patent No. 2802878 or U.S. Pat. No. 5,478,639).
While these implosion-proof tapes are being widely used at the current time for implosion proofing of cathode-ray tubes, they are all common adhesive tapes (or tacky or pressure sensitive adhesive tapes) prepared by applying a hot-melt adhesive layer or, onto the entire surface of a base made of a continuous resin film, a pressure-sensitive adhesive layer.
FIG. 1 shows an example of a cathode-ray tube that has been implosion-proofed using this type of implosion-proof adhesive tape. A metal clamping band 3 is shrink-fitted around the perimeter of the side wall of a glass cathode-ray tube 1 via adhesive tape 2. The cathode-ray tube is mounted in a television set or monitor casing (not shown) by a fitting piece 4 mounted on the metal clamping band 3. FIG. 2 shows an outer view of an example of a conventional cathode-ray tube in more detail. The cathode-ray tube is formed by bonding together funnel glass 5 and a glass panel 6 with frit glass 7. The metal clamping band 3 is fitted around the mold match line 8 created during the panel manufacturing step by heating to near the yield point for expansion and insertion and then allowing to cool for clamping by contractile force to provide reinforcement.
With the increasing sizes of cathode-ray tubes and the widening uses of displays in recent years, the spherical surface panel shape of the traditional common cathode-ray tube is gradually being supplanted by completely flat surface shapes or flat surface-type cathode-ray tubes that employ panels with a very nearly flat curvature. Such flat panels have the advantage of no external reflection and also allow easier surface working such as electrical conductive working to eliminate static electricity, or anti-glare working; their production is therefore increasing for large-sized tubes and display tubes.
Flat panels have a higher outer side surface than conventional panels because of their panel structure, while the panel production necessitates an increase in the outer perimeter side angle from the conventional 1xc2x0 to 5xc2x0, for example, as a square pyramid with the surface direction as the apex.
Because of the increased height of the panel outer side with respect to conventional panels, the lug mounting position on the cathode-ray tube cabinet must be much farther to the front than conventional spherical cathode-ray tubes, and since the lug is welded to the metal clamping band, it has been necessary to effect implosion-proof reinforcement at the section near the front of panel outer side surfaces with a large angle and without any such engagement point as the aforementioned mold match line.
When implosion-proof tape with the conventional adhesive layer is applied on this section, considerable slippage occurs due to the clamping force caused by cooling contraction of the clamping band that has been expanded by heating, due to fluidity of the adhesive of the implosion-proof tape when it melts and, in severe cases, the reinforcing band may inconveniently fall off together with the implosion-proof tape.
The present invention, as the result of diligent research aimed at overcoming the problems described above and investigation of the nature of implosion-proof tape for cathode-ray tubes, is the successful development of a cathode-ray tube implosion-proof tape which is economical by comprising only the essential indispensable elements for a cathode-ray tube implosion-proof tape, and which has a completely new structure that provides improved slip properties.
It is therefore an object of the present invention to provide an economical cathode-ray tube implosion-proof tape that comprises only the essential indispensable elements for cathode-ray tube implosion-proofness with no unnecessary components, and which has the necessary adhesive property with excellent slip properties, as well as an implosion-proof method and an implosion-proof cathode-ray tube employing the tape.
As a result of much diligent research directed toward achieving this object, the present inventors have completed the present invention upon finding the following: The cause of slippage between the metal clamping band and the cathode-ray tube is the fact that the hot-melt adhesive bonding together the glass of the cathode-ray tube and the metal clamping band, the pressure-sensitive adhesive layer for attachment of the implosion-proof tape to the cathode-ray tube, or the tape substrate covered with the hot-melt adhesive, is a continuous layer. A small amount of hot-melt adhesive is sufficient to bond together the metal clamping band and the cathode-ray tube, and therefore that a needless amount of continuous film-like adhesive tape has been used according to the prior art. A suitable fabric-like base matrix instead of granules in a non-continuous dispersion state is suitable to avoid slipping between the metal clamping band and the cathode-ray and damage to the surface of the cathode-ray tube. Moreover, it was also found that if the cathode-ray tube implosion-proof mesh tape is constructed by using a mesh-like fabric as the tape substrate or backing and applying, to the mesh-like substrate, only the absolute minimum necessary amount of hot-melt adhesive and pressure-sensitive adhesive, the cathode-ray implosion-proof tape will consist of only the absolute minimum necessary elements, thus eliminating unnecessary material to not only contribute to lower cost and lighter weight, but also to avoid inhibition of other functions by these extra constituents, for more excellent performance.
The present invention therefore provides the following:
(1) An adhesive mesh tape for preventing implosion of a cathode-ray tube, comprising
a fabric of yarns in the form of mesh having first and second main surfaces;
a hot-melt resin provided on all or a portion of the surface of said fabric; and
a pressure-sensitive adhesive disposed on said first main surface of said fabric.
(2) The adhesive mesh tape according to (1), wherein the total volume of said hot-melt resin and said pressure-sensitive adhesive is less than the volume of the open space of said fabric; so that all said hot-melt resin and said pressure-sensitive adhesive can be incorporated into said open space of said fabric when said adhesive mesh tape is clamped between a cathode-ray tube and a metal clamping band.
(3) The adhesive mesh tape according to (2), wherein the total volume of said hot-melt resin and said pressure-sensitive adhesive is not more than three fourths of the volume of the open space of said fabric.
(4) The adhesive mesh tape according to (3), wherein the total volume of said hot-melt resin and said pressure-sensitive adhesive is not more than the half of the volume of the open space of said fabric.
(5) The adhesive mesh tape according to (1)-(4), wherein at least wefts of said fabric are glass yarns.
(6) The adhesive mesh tape according to (1)-(5), wherein at least part of said fabric is colored black.
(7) The adhesive mesh tape according to (1)-(6), wherein said fabric has a compression breaking strength of not less than 5 kgf/cm.
(8) The adhesive mesh tape according to (1)-(7), wherein said fabric comprises wefts and warps at a density in a range of 5 to 50 yarns per 25 mm and said yarns have a thickness in a range of 50 to 1300 denier.
(9) The adhesive mesh tape according to (1)-(8), wherein said hot-melt resin is coated on said fabric in an amount of 5 to 40 g/m2.
(10) A method for reinforcing a cathode-ray tube to prevent an implosion thereof, said method comprising
preparing a cathode-ray tube having a peripheral portion and covered with a transparent electrically conductive film;
winding an adhesive tape according to claim 1 completely or partly on the peripheral portion of the cathode-ray tube; and
clamping the cathode-ray tube with a metal clamping band around the peripheral portion of the tube and on top of the adhesive tape, by heating the metal clamping band to a temperature of not less than 60xc2x0 C. and placing the metal clamping band around the adhesion tape and then cooling the metal clamping band to fix the adhesive tape to the peripheral portion of the tube by the metal clamping band.
(11) The method according to (10), wherein said cathode-ray tube has a flat front surface.
(12) The method according to (11), wherein said peripheral portion of said cathode-ray tube has an inclination angle of more than 5xc2x0.
(13) A cathode-ray tube comprising a cathode-ray tube body having a peripheral glass portion and covered with a transparent electrically conductive film;
a metal clamping band wound around said peripheral portion of said tube; and
an adhesive mesh tape according to claim 1, lying between said cathode-ray tube and said metal clamping band, wherein all or most of the yarns of said fabric are in direct contact with the glass surface of said tube and/or the metal surface of said metal clamping band and said glass surface of said tube and said metal clamping band are bonded together with the hot-melt resin either through or not through said fabric yarns therebetween.
(14) The cathode-ray tube according to (13), wherein said cathode-ray tube has a flat front surface.
(15) The cathode-ray tube according to (14), wherein said peripheral portion of said cathode-ray tube has an inclination angle of more than 5xc2x0.